Altered patterns of senescence and ripening in gf, a stay-green mutant of tomato (Lycopersicon esculentum Mill.)

Abstract

Key words: Carotenoids, chlorophyll, ripening, senescence, tomato. The gf tomato mutant, which retains chlorophyll during ripening, has been found to be affected in leaf senes-

The Senescence-Induced Staygreen Protein Regulates Chlorophyll Degradation

“…During dark-induced senescence, green Chl catabolites, Chlide a and Pheide a, accumulate in the senescent leaves of sgr to higher levels than in wildtype leaves (Figure 2). In this respect, we conclude that the rice sgr mutant has the same characteristics as other nonfunctional type C stay-green mutants from F. pratensis, P. vulgaris, tomato, and pepper, which also accumulate significant amounts of Chlide a and/or Pheide a in their senescing leaves (Vicentini et al, 1995;Fang et al, 1998;Akhtar et al, 1999;Roca and Mínguez-Mosquera, 2006).…”

“…Since the photosynthetic competence of sgr leaves decreases normally during that period, it is classified as one of the nonfunctional type C stay-green mutants. To date, type C mutants have been reported in several plants: the senescenceinduced deficiency (sid) mutant in Festuca pratensis (Thomas and Stoddart, 1975); the cytG and d 1 d 2 mutants in soybean (Guiamé t et al, 1991); the green flesh mutant in tomato (Solanum lycopersicum) (Cheung et al, 1993;Akhtar et al, 1999); the nonyellowing mutants in Phaseolus vulgaris (Fang et al, 1998) and Dendranthema grandiflora (Reyes-Arribas et al, 2001); the oresara10 (ore10) mutant in Arabidopsis thaliana (Oh et al, 2000); and the chlorophyll retainer mutant in pepper (Capsicum annuum) (Efrati et al, 2005).…”

Stay-green protein, defective in Mendel’s green cotyledon mutant, acts independent and upstream of pheophorbide a oxygenase in the chlorophyll catabolic pathway

“…This is demonstrated by the high number of reports about identification of sgr/sid mutants and the recent cloning of SGR/SID genes from Arabidopsis, Festuca/Lolium, pea and rice (Armstead et al, 2006;Armstead et al, 2007;Jiang et al, 2007;Park et al, 2007;Ren et al, 2007;Sato et al, 2007). It is likely that additional stay-green mutants, such as tomato green flesh (gf; Akhtar et al, 1999) and pepper chlorophyll retainer (cl; Efrati et al, 2005) are defective in SGR as well. Only some of these mutants have been attributed to the class of type C non-functional stay-greens.…”

Different Mechanisms Are Responsible for Chlorophyll Dephytylation during Fruit Ripening and Leaf Senescence in Tomato

“…(Amir-Shapira et al, 1987;Trebitsh et al, 1993;Jacob-Wilk et al, 1999;Azoulay Shemer et al, 2008), where leaf senescence-related chlorophyll breakdown has not been studied in detail (Katz et al, 2005). We chose tomato as a model because, besides a rather short life cycle, it offers established genetic tools as well as well-defined methods for fruit ripening and leaf senescence analysis (Akhtar et al, 1999;Barry et al, 2008) and, thus, allowed the simultaneous analysis of dephytylation during leaf senescence and fruit ripening (Figs. 6 and 7).…”

“…Deficiency of SGR, as for example in the tomato green flesh (gf) and the red pepper (Capsicum annuum) chlorophyll retainer mutants, causes a stay-green phenotype of these mutants in leaves and fruits (Barry et al, 2008;Borovsky and Paran, 2008), indicating that SGR is required for chlorophyll breakdown in both tissues. Similarly, PAO and RCCR were found to be active in chromoplast membranes isolated from tomato and red pepper fruits Akhtar et al, 1999), and recently, different fluorescent and nonfluorescent phyllobilins were shown to occur in ripening apple (Malus domestica), pear (Pyrus communis), and banana (Kräutler, 2008;Moser et al, 2009). Finally, SGR and PAO have been identified in a recent proteome analysis of tomato chromoplasts .…”